parasitism

Deep research

Generated by just research-trait; source: research/traits/ecology/parasitism-deep-research-falcon.md

# TraitMech curation report: microbial parasitism

## Executive curation recommendation

**Target:** parasitism (`traitmech:000043`; ECOLOGY; CLASS; REVIEWED).

The trait should represent an **ecological interaction outcome**, not a single virulence pathway: the microorganism obtains resources or reproductive benefit from a host while causing a net reduction in host fitness. The most defensible cross-taxon graph is therefore a small backbone—host association/colonization → host-resource access → microbial maintenance or reproduction, together with host damage or resource diversion → reduced host survival/reproduction—supplemented by explicitly taxon-specific mechanistic modules.

The literature treats host–microbe effects as a continuum rather than immutable categories. Pathobionts, for example, can move between harmless and harmful states depending on host immunity and microbiota composition; temperature, transmission route, and community context can also change the interaction outcome. Host-cell lysis and resource theft leading to castration are clear parasitic endpoints. Thus, a mechanism should not be sufficient by itself to assign this trait unless host-fitness harm is demonstrated or strongly established for the association. (drew2021microbialevolutionand pages 11-12)

## 1. Scope and boundaries

### Inclusion criterion

Curate `traitmech:000043` when evidence supports both:

1. **Microbial benefit:** resource acquisition, energy acquisition, persistence, growth, reproduction, or transmission derived from the host; and
2. **Host cost:** reduced survival, fecundity, growth, physiological performance, or another defensible component of host fitness.

Obligate intracellular bacterial parasites are a strong mechanistic subset: they require invasion of a eukaryotic cell to reproduce, occupy cytosolic or vacuolar niches, commonly show genome reduction, and scavenge costly metabolites rather than synthesizing them de novo. These properties explain dependence and exploitation, but host dependence alone still does not establish the ecological fitness cost. (mandel2024metabolismandphysiology pages 1-2)

### Nearby traits that should remain distinct

- **Mutualism:** both partners have a net fitness benefit under the measured conditions.
- **Commensalism:** the microbe benefits while no significant host-fitness effect is detected.
- **Pathogenicity/virulence:** capacities to cause disease or damage. These are frequent mechanisms or manifestations of parasitism, but disease is neither required nor by itself proof of an evolutionary fitness cost.
- **Pathobiont:** a context-dependent state, not a constitutively parasitic class. The same organism may be commensal under one immune/community environment and harmful under another. (drew2021microbialevolutionand pages 11-12)
- **Obligate host dependence:** inability to reproduce without a host. This supports parasitic resource dependence but does not distinguish a harmful parasite from an obligate mutualist.
- **Predation:** normally involves killing and consuming multiple prey individuals rather than sustained exploitation of a host association. Lytic phages are a boundary case; include only if TraitMech’s operational scope treats viral infection as microbial parasitism.
- **Parasitoidism/parasitic castration:** host reproduction is eliminated and resources are redirected to the exploiter. This is an extreme, readily measurable parasitic fitness cost; *Pasteuria*–*Daphnia* is a microbial example. (drew2021microbialevolutionand pages 11-12)

### Assay recommendation

A trait assertion should record: host taxon, microbial strain, infection stage, environment, comparator, microbial benefit endpoint, and host-fitness endpoint. Suitable host endpoints include survival, lifetime fecundity, offspring number, growth, or competitive performance. Cell death, cytokine induction, metabolite depletion, or clinical symptoms are useful intermediate nodes but should not automatically be equated with organismal fitness.

## 2. Candidate nodes grouped by type

### Trait and outcome nodes

- parasitism — `traitmech:000043`
- host-derived resource acquisition — label-only
- microbial intracellular growth/replication — label-only pending GO review
- microbial transmission — label-only
- host cellular damage; host-cell lysis — label-only
- host metabolic dysbiosis — label-only
- reduced host survival; reduced host reproduction; host castration; host fitness cost — label-only
- parasite–mutualist continuum; context-dependent pathobiont state — label-only

### Organisms and cellular niches

Candidate taxon nodes, requiring NCBITaxon lookup during YAML implementation: *Chlamydia trachomatis*, *C. muridarum*, *Coxiella burnetii*, *Rickettsia prowazekii*, *Neisseria gonorrhoeae*, *Staphylococcus aureus*, *Plasmodium* spp., *Toxoplasma gondii*, *Cryptosporidium* spp., *Trypanosoma brucei*, *T. cruzi*, and *Leishmania donovani*.

Compartments include the chlamydial inclusion/inclusion membrane, acidic Coxiella-containing vacuole (CCV), host cytosol, lysosome-derived compartment, erythrocyte, hepatocyte, intestinal epithelial cell, Golgi, endoplasmic reticulum, multivesicular body, mitochondrion, and apicoplast. Leave these label-only until exact GO or host-cell ontology terms are verified.

### Genes, proteins, and complexes

- Chlamydial inclusion effectors: IncA, IncD, IncE/CT116, IncF, IncG, CT229, CT442, CT449, CT622/TaiP, CT813/InaC, Cpn0585.
- Host trafficking machinery: Rab1, Rab4, Rab6, Rab10, Rab11, Rab14, Rab35, Rab39; ARF1/ARF4; GBF1; CERT; FIP2; RUFY1; BICD1; SNAP-23; syntaxins 4/10; VAMP3/4.
- Energy and metabolic functions: ATP/ADP translocase/Npt1; GpsA; hexokinase II; p53; HIF1α; YtgR; FeoAB.
- Coxiella virulence machinery: Dot/Icm type IVB secretion system and its effectors; eIF2α/UPR host targets.

Showing the first 60 of 228 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.